1. Field of the Invention
The present invention concerns a pressurization and filter installation, notably for shelters designed to protect personnel against the effect of nuclear, biological and chemical weapons, with sealing means containing and protecting the shelter interior against overpressures and underpressures due to explosions.
2. Description of the Prior Art
While existing installations of this type have proved satisfactory, our work has shown that they nevertheless have certain disadvantages.
The equipment filtering the air entering the interior of the shelter is situated inside the shelter, with the occupants. This arrangement involves the hazard of the occupants being irradiated when the filter has absorbed a large quantity of radioactive dust or iodine. Means are available for overcoming these disadvantages, but for the most part these consist in protective devices which must be added to the filter batteries. These are generally relatively expensive.
The shelter is isolated from the outside by the provision of two trapdoors, one of which is thermally insulative, disposed in a vertical access shaft leading into an airlock communicating with the interior of the shelter through an armoured door. Sanitary facilities are normally disposed in this airlock. If these two barriers are damaged as the result of an explosion, only the armoured door continues to provide isolation from the outside. If the sealing of the latter leaves something to be desired, toxic gases may infiltrate into the shelter, representing a danger to the health of its occupants. Also, the sanitary facilities in the airlock remain inaccessible, at least temporarily, being exposed to a contaminated atmosphere.
It should also be mentioned that pressurization and filter installations already available for shelters designed to protect a few dozen persons leave a great deal to be desired in respect of the arrangement and effectiveness of the airlocks. No decontamination means are provided for use after a reconnaissance patrol carried out by a few occupants, and contaminated air admitted into the airlock may in turn contaminate the atmosphere in the shelter.
The present invention is directed towards a combination of arrangements providing for a significant improvement in the effectiveness of pressurization and filter installations for shelters designed to protect a few dozen persons against the effects of nuclear, biological and chemical (NBC) weapons.